1. Field of the Invention
The invention relates to an amplifier which is capable of balancing voltages at differential nodes of the amplifier when the amplifier is turned off, and more particularly to a transceiver device using the same.
2. Description of the Related Art
In a transceiver device, a transmitter generates output signals for an antenna unit, and the antenna unit generates a radio frequency (RF) output signal for transmission. The antenna unit receives an RF input signal to generate input signals. An amplifier in a receiver coupled to the antenna unit receives and amplifies the input signals. The other circuits in the receiver, such as mixers, filters, and analog-to-digital converters, then processes the amplified input signal for back-end circuits. Generally, before the transceiver device leaves the factory, the performance of the transmitter and the receiver may be determined through an attenuator between the transmitter and the receiver. In the test mode, the output signals generated by the transmitter are weakened by the attenuator, and the attenuated output signals are received by the receiver. At this time, the amplifier is turned off. Note that the output signals generated by the transmitter may induce leakage current in the amplifier due to unbalanced voltages at differential nodes of the amplifier. The leakage current may disadvantageously affect the attenuator, resulting in an inaccuracy in the performance determination.
Thus, it is desired to provide an amplifier which is capable of balancing voltages at differential nodes of the amplifier when the amplifier is turned off.